Explosive composition for bonding containing an organo metallic polymer

ABSTRACT

A HIGHLY SENSITIVE EXPLOSIVE HAVING A LOW DETONATION VELOCITY FORMED FROM A HOMOGENEOUS MIXTURE OF A HEAVY METAL OXIDE SUCH AS LEAD OXIDE (PBO) AND A POLYHYDROXY COMPOUND SUCH AS GLYCEROL. THE RESULTING NOVEL EXPLOSIVE IS OF PARTICULAR ADVANTAGE WHEN MIXED WITH COMMERCIAL EXPLOSIVES AND UTILIZED IN THE HIGH ENERGY BONDING OF TWO OR MORE METALLIC MEMBERS SUCH AS IN THE FORMATION OF HONEVCOMB OR OTHER METALLIC STRUCTURES.

May 1,1973 R. H. VELTEN 3,730,791

7 EXPLOSIVE COMPOSITION FOR BONDING CONTAINING AN ORGANOMETALLIC POLYMER Filed July 16, 1971 DETONATION Vnocnv (1o? fl/atc O 10 2O 3O 4O 5O 6O 7O 8O %PbOGLYctQoL (bv Wmem) *HoTt; txpLoslvt DEFLAGQATES Roman H. Vmeu INVENTOR.

M: 11 m1 Z uvm/d' I i i United States Patent m 3,730,791 EXPLOSIVE COMPOSITION FOR BONDING CON- TAINING AN ORGANO METALLIC POLYMER Robert H. Velten, Boulder, Colo., assignor to E. F. Industries, Inc., Louisville, Colo. Filed July 16, 1971, Ser. No. 163,156 Int. Cl. C06b 1/04 US. Cl. 149-46 Claims ABSTRACT OF THE DISCLOSURE A highly sensitive explosive having a low detonation velocity formed from a homogenous mixture of a heavy metal oxide such as lead oxide (PbO) and a polyhydroxy compound such as glycerol. The resulting novel explosive is of particular advantage when mixed with commercial explosives and utilized in the high energy bonding of two or more metallic members such as in the formation of honeycomb or other metallic structures.

The present invention is directed to a novel composition of matter that has a low detonation velocity when employed as a highly sensitive explosive.

The use of shock waves created such as by conventional secondary solid explosives is achieving greater acceptance for the formation and joining of metal. Such explosive welding for bonding metal sheets or foils together has a number of advantages over joining methods previously developed. Principally, explosive welding eliminates the necessity for an intermediate material such as a brazing metal or an adhesive which limits the structural characteristics of the ultimate material formed therefrom. Furthermore, the bond produced between a pair of members by explosive welding can be as strong as the members themselves. In addition, conventional explosive welding involves substantially reduced fabrication time. Again, the use of explosive Welding permits the bonding of certain elements together that have not heretofore been possible because of oxides existing or reactions taking place during conventional welding processes. Typical methods of utilizing explosives for this purpose are described in US. Pats. Nos. 3,031,746, 3,036,373, 3,137,937, 3,264,371 and 3,449,819.

Up to the present time, conventional explosives such as trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN), ammonium nitrate, nitrostarch, nitroglycerine, cyclomethylene trinitramine and the like have been utilized for accomplishing the explosive welding. These explosives are commonly referred to as secondary explosives because of the need to activate them with a primary explosive such as lead azide or mercury fulminate in the form of an initiator, i.e., a blasting cap, detonating fuse and the like. Such conventional explosives have a detonation velocity of at least 13,000 or 14,000 feet per second and can be modified to some degree by mixing with inert diluents such as sodium chloride, sodium nitrate and the like. Detonation velocity varies with the type of explosive involved so that mixtures with various inert diluents have heretofore been used to modify the detonation velocity. In the explosive bonding of plural stacks of metallic sheets, it has long been desirable to develop an explosive having a detonation velocity in the range of 10,000 feet per second or less.

It has now been found that organo-metallic compounds formed from heavy metal oxides, such as lead oxide (PbO), and organic polyhydroxy compounds, combined in various proportions, provide a secondary explosive having a detonation velocity as low as about 6500 feet per second. More particularly, it has now been found that when the aforementioned conventional explosives are combined with various proportions of heavy metal oxide 3,730,791 Patented May 1, 1973 and polyhydroxy compounds, an explosive having a substantially reduced detonation velocity is obtained while maintaining explosive sensitivity, shock wave propagation and energy content. Such novel explosive combinations exhibit detonation velocities in the range of 9,000 to 10,000 feet per second, a detonation velocity not presently available with conventional solid explosives.

Although it is not intended that the present invention be limited to any specific theoretical concept, it appears that formation of the novel compositions of this invention result when a heavy metal oxide reacts with a polyhydroxy compound by displacing a hydrogen atom from a primary hydroxyl group in each of two polyhydroxy molecules. This reaction then expands to form a polymer system whereint he heavy metal oxide is interspersed in the long chain organic backbone. Typical of this reaction is thought to be the following illustrating the reaction of lead oxide (PbO) with glycerol:

The term polyhydroxy organic compound is intended V to include the glycols, triols and tetrahydroxy compounds having up to 10 carbon atoms. Typical examples include ethylene glycol, propylene glycol, and butylene glycol with glycerol being preferred. A preferred range of carbon atoms is from 3 to 6 carbons. Suitable heavy metal oxides include those wherein the metal has an atomic number of 22 to 82, inclusive. Metals defined by Groups IV-B, V-B, VI-B, VII-B, and IV-A of the Periodic Table of Elements, and especially those found in Group V-A are advantageous. Lead is preferred.

Although a stoichiometric mixture of the lead oxide and polyhydroxy compound is preferable, advantageous explosive characteristics have been obtained when either component was present in the amount up to 60% by molecular weight. When greater or lesser amounts of lead oxide are employed, it has been found that the ultimate composition can be inhibited by unpolymerized material remaining and cause resultant desensitization of the explosive. Although the ultimate explosive mixture is preferably in a solid form, slurries are also useful.

To further illustrate the novel aspects of the invention, the following examples are provided. It should be understood that the details thereof are not to be regarded as limitations as they may be varied as will be understood by one skilled in this art.

EXAMPLE I Pentolite*--Lead oxide and glycerol A pentolite-containing explosive was prepared in approximately the following proportions:

Constituent: Weight percent Pentolite 60 Finely divided aluminum powder 1 PbO-glycerol reaction mix 39 *Prepared by the Wyler Process containing 50% TNT and 50% PETN and available from the TroJan Powder tlompany.

apart transverse strips of polyvinyl acetate-base adhesive (stop-weld) having a thickness of 200 microinches by a rotogravure method and thereafter cut into three hundred 3-foot sections (sheets). The 300 sheets were stacked as a single pile with the strips of stop-weld staggered so that node regions would be formed on the opposite side of each sheet from where the strip was disposed. This arrangement was employed to form conventional hexagonal honeycomb upon completion of the process. A pressure of 20 pounds per square inch gauge was applied at a temperature of 200 F. for /2. hour to cure the stopweld strips and cause them to adhere to adjacent surfaces of the sheets. The resulting stack was cooled for 4 hours at one pound per square inch gauge pressure.

A 6061 aluminum sheet (20 mil x 3 feet x 6 inch) and a 75A titanium sheet (12 mil x 3 feet x 6 inch) were bonded to the top of the stack and to each other with room temperature rubberbase adhesive. A steel layer (1 inch x 36 inch x 6 inch) was bonded to the bottom of the stack with rubberbase adhesive. The entire unit was transferred to a bonding pad consisting of a 3 inch x 6 inch x 36 inch steel cold-rolled anvil. The stack was leveled by leveling the uppermost steel layer. An explosive slurry tray was formed of a cold-rolled steel plate (0.089 inch x 30 inch x 42 inch) and a inch high plywood barrier was arranged around the perimeter thereof to form a shallow trough. The tray was supported on a pile of sand so that one end extended over and was spaced from the pressed stack of sheets by a stand-off of /2 inch. The majority of the tray was supported by the pile of sand so as to be free standing with respect to the pressed stack. The tray was leveled and sufficient of the explosive described supra, was spread onto the tray to fill it to the level defined by the quarter inch deep plywood edges. A detonation cap was disposed in the tray at the end farthest from the stacked sheet. The cap was ignited and the charge detonated. It was noted that the ambient temperature prior to detonation was 40 F.

An examination of the resulting structure revealed that bonding was superior throughout the stack and bond strengths were consistent with the calculated energies of the explosive.

EXAMPLE II Nitrostarch/ammonium nitrateLead oxide and glycerol slurry A nitrostarch-containing explosive slurry was prepared in approximate by the following proportions:

Constituent: Weight percent The slurry was mixed and employed in the manner set forth in Example I except the explosive was able to be poured onto the tray. The detonation velocity thereof was approximately by 12,500 ft./sec. Due to the self-leveling effect and the better homogeneity of the constituents of the explosive, bond strengths were superior to those obtained in Example I.

Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it is understood that certain changes and modifications may be practiced within the spirit of the invention as limited only by the scope of the appended claims.

What is claimed is:

1. A low detonation velocity explosive composition comprising the mixture of a major quantity of commercial explosive selected from the group consisting of trinitrotoluene, pentaerythritol tetranitrate, ammonium nitrate, nitrostarch, nitroglycerine, and cyclomethylene trinitramina and a minor quantity of an organo-metallic polymer formed as the reaction product of lead oxide and a polyhyd'roxy organic compound having from two to ten carbon atoms, the amount of lead oxide being from about 40 percent to about percent based on total moles.

2. A novel composition in accordance with claim 1 wherein the commercial explosive is pentaerythritol tetranitrate.

3. A composition in accordance with claim 1 wherein the polyhydroxy organic compound is selected from diols, triols, and tetraols including up to 10 carbon atoms.

4. A composition in accordance with claim 3 wherein the polyhydroxy compound is a triol of 3 to 5 carbon atoms.

5. A composition in accordance with claim 4 wherein the triol is glycerol.

References Cited UNITED STATES PATENTS 3,290,343 12/1966 Stone et a1. 149109 X 3,115,526 12/1963 DAlelio 149109 X 3,262,956 7/1966 Kenney 149-24 X 3,293,091 12/1966 Kenney 14924 STEPHEN J. LECHERT, JR., Primary Examiner US. Cl. X.R. 

